Speech enhancement using a frequency-specific composite Wiener function

This paper introduces a new speech enhancement approach based on the design of a frequency-specific composite gain function for Wiener filtering. Motivated by the recently established finding that the acoustic cues at low frequencies can improve speech recognition in noise by the combined electric and acoustic stimulation technique, a less aggressive gain function is applied to replace the Wiener filter´s conventional rigid gain function at low frequencies. With this modification, the proposed approach is able to recover more low frequency (LF) components and enhance the speech quality in noisy environments. An adaptive procedure is utilized to determine the low frequency boundary. Objective evaluation, based on the PESQ measure, revealed that the proposed approach with adaptive LF boundary improved significantly the PESQ scores compared to the scores obtained with the conventional Wiener filter in steady-state noise, white noise and babble interference conditions. Speech quality was also found to be significantly enhanced in the car noise conditions when the less aggressive gain function was selectively applied only to the consonants.